<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box {
          border: 3px solid #000000;
          border-radius: 10px;
          padding: 20px;
          margin: 20px;
          width: 200px;
        }
        h3 {
          margin: 10px 0 20px 0;
        }
        p {
          margin: 20px;
        }
      </style>
</head>
<body>
    <div id="app">
        <div class="box">
          <h3>小黑自动售货机</h3>
          <button @click="buy(5)">可乐5元</button>
          <button @click="buy(10)">咖啡10元</button>
          <button @click="buy(8)">牛奶8元</button>
        </div>
        <p>银行卡余额：{{ money }}元</p>
      </div>
    
      <script src="https://cdn.jsdelivr.net/npm/vue@2/dist/vue.js"></script>
      <script>
        const app = new Vue({
          el: '#app',
          data: {
            money: 100
          },
          methods:{
            buy(price){
                this.money -= price
            }
          }
        })
      </script>
</body>
</html>